Fortunately, we have never found ourselves in a position in which we seriously had to consider any kind of ART. When we experienced a period of time where we had difficulty trying to conceive, we already had two children, so we ultimately decided that if we were unsuccessful that we would be thankful for the children we already had. We have had friends who have faced decisions about ART, though, and it has not been easy for them.
In our church, it seems (from all outward appearances anyway) that the majority of couples and families have not experienced great difficulties conceiving children. It seems as though every few weeks, a new pregnancy is being publicly announced. This is a great blessing for which we are always thankful to God, but when this happens, it's easy to take for granted that having children is just a matter of choice, or what all good Christian families should be doing. The command to "be fruitful and multiply," "filling your quiver" and all that.
But in the midst of all this, it has sometimes seemed to me that it is those people who have not had difficulties having children who are quick to take the simplistic view that IVF or other forms of ART are wrong from a Christian standpoint. For those who desperately want children and are unable to have them, this can be very hurtful to hear. The reflections in Izaac's post are really helpful in challenging this view.
A book is coming out soon on the ethics of ART by Dr Megan Best, an Australian Christian bioethicist who has also written extensively on palliative care/death and dying. It has a catchy title :"Fearfully and wonderfully made."
I'm looking forward to reading it.